vintage sweetheart jewelry

not sewing related per se, but all about the accessories. i discovered "sweetheart" jewelry this weekend while reading janie bryant's (janie is the costume designer for "mad men") book on style.

does anyone here have experience with this style of jewelry? know some of the history? i know by the late 40s and through the 60s it was more traditional, the sort of thing you gave your 'steady', while in the early 40s, during the war, they were more related to the different branches of the armed services.